System for controlling active suspensions of a vehicle

Abstract

In a system for controlling active suspensions of a motor vehicle, having fluid suspensions for the respective wheels, a longitudinal acceleration sensor, control valves for the respective suspensions, and a controller for adjusting the control valves to charge and discharge a fluid into and out of the fluid suspensions so as to control the vehicle attitude, a hysteresis circuit is provided to receive a longitudinal acceleration signal from the acceleration sensor, for hysteresis processing of the signal, whereby microvibration components included in the acceleration signal is removed. The width of hysteresis is increased as the vehicle speed increases because the amplitude of microvibration becomes larger as the vehicle speed increases. For more stable vehicle attitude control, a dead-zone circuit is provided to cut fluctuations of the hysteresis-processed signal within a specific width in the vicinity of zero.

What is claimed is: 
     
       1. A system for controlling an active suspension of a vehicle, having fluid suspensions provided for respective wheels and valve means for charging and discharging the fluid into and out of the respective fluid suspensions to extend and contract the suspensions independently, comprising: vehicle speed sensing means for sensing vehicle speed and for generating a vehicle speed signal indicative of the vehicle speed;   acceleration sensing means for detecting acceleration of the vehicle and for generating an acceleration signal indicative of the acceleration;   hysteresis means for smoothing said acceleration signal by processing said acceleration signal with a predetermined hysteresis width;   hysteresis width changing means responsive to said vehicle speed signal for changing said predetermined hysteresis width based on the magnitude of said vehicle speed, said predetermined hysteresis width being set wider as said vehicle speed becomes larger; and   controlling means responsive to an acceleration signal processed by said hysteresis means for controlling said valve means to adjust an amount of the fluid to be charged and discharged in said suspensions so as to control the vehicle attitude.   
     
     
       2. The system according to claim 1, wherein said hysteresis width changing means is adapted to vary said hysteresis width linearly with said vehicle speed. 
     
     
       3. The system according to claim 1, wherein said hysteresis width changing means is adapted to vary said hysteresis width gradually with said vehicle speed. 
     
     
       4. The system according to claim 1, wherein said hysteresis width changing means is adapted to vary said hysteresis width stepwise with said vehicle speed. 
     
     
       5. The system according to claim 1, wherein said acceleration sensing means is a longitudinal G-sensor for detecting longitudinal acceleration of the vehicle. 
     
     
       6. The system according to claim 5, further comprising: dead zone means for cutting the fluctuations of said acceleration signal processed by said hysteresis means within a predetermined dead zone width in the vicinity of zero.   
     
     
       7. The system according to claim 6, further comprising: dead zone width changing means responsive to said vehicle speed signal for changing said predetermined dead zone width based on the magnitude of said vehicle speed, said predetermined dead zone being set wider as said vehicle speed becomes larger.   
     
     
       8. The system according to claim 7, wherein said dead zone width changing means is adapted to set said predetermined dead zone width wider than said predetermined hysteresis width. 
     
     
       9. The system according to claim 7, further comprising: producing means for producing a desired vehicle height signal;   longitudinal load shaft quantity calculating means responsive to output signal from said dead zone means and said vehicle height signal for calculating a longitudinal load shift quantity;   suspension reaction force variation calculating means responsive to output signal from said longitudinal load shift quantity calculating means for calculating a variation in the reaction force of each of said suspensions; and   control quantity calculating means responsive to output signal from said suspension reaction force variation calculating means for calculating a control quantity to adjust said valve means.   
     
     
       10. The system according to claim 9, further comprising: a lateral G-sensor provided on the vehicle for detecting lateral acceleration of the vehicle and for generating a lateral acceleration signal indicative thereof;   second hysteresis means for smoothing said lateral acceleration signal by hysteresis-processing thereof;   second dead zone means for cutting the fluctuations of output signal from said second hysteresis means in the vicinity of zero;   rolling moment calculating means responsive to said vehicle height signal and output signal from said second dead zone means for calculating a rolling moment;   rolling moment distribution ratio setting means responsive to said vehicle speed signal for setting a front-read rolling moment distribution ratio;   lateral load shift quantity calculating means responsive to output signals from said rolling moment calculating means and said rolling moment distribution ratio calculating means, for calculating a lateral load shift quantity and for generating a lateral load shift quantity signal indicative thereof; and   second suspension reaction force variation calculating means responsive to output signal from said lateral load shift quantity calculating means, for calculating a variation in the reaction force of each suspension, whereby said control quantity calculating means is responsive to output signal from said second suspension reaction force variation calculating means for calculating said control quantity.   
     
     
       11. The system according to claim 10, further comprising: second hysteresis width changing means for changing a second predetermined hysteresis width applied to said lateral acceleration signal based on the magnitude of said lateral acceleration signal detected by said lateral acceleration sensor, said second predetermined hysteresis width being set wider as said lateral acceleration increases.   
     
     
       12. A system for controlling an active suspension of a vehicle, having fluid suspensions provided for respective wheels, valve means for charging and discharging the fluid into and out of the respective fluid suspensions to extend and contract the suspensions independently, comprising: acceleration sensing means for detecting acceleration of the vehicle and for generating an acceleration signal indicative of the acceleration;   hysteresis means for smoothing said acceleration signal by processing said acceleration signal with a predetermined hysteresis width;   hysteresis width changing means responsive to said acceleration signal for changing said predetermined hysteresis width based on the magnitude of said acceleration, said predetermined hysteresis width being set wider as said acceleration is larger; and   controlling means responsive to an acceleration signal processed by said hysteresis means for controlling said valve means to adjust an amount of the fluid to be charged and discharged in said suspensions so as to control the vehicle attitude.   
     
     
       13. The system according to claim 12, wherein said acceleration sensing means is a lateral G-sensor for detecting lateral acceleration of the vehicle. 
     
     
       14. The system according to claim 13, further comprising: dead zone means for cutting the fluctuations of said acceleration signal processed by said hysteresis means within a predetermined dead zone width in the vicinity of zero.   
     
     
       15. The system according to claim 14, further comprising: producing means for producing a desired vehicle height signal;   vehicle speed sensing means for sensing vehicle speed and for producing a vehicle speed signal indicative of said vehicle speed;   rolling moment calculating means responsive to said vehicle height signal and output signal from said dead zone means for calculating a rolling moment; rolling moment distribution ratio setting means responsive to said vehicle speed signal for setting a front-rear rolling moment distribution ratio;   lateral load shift quantity calculating means responsive to output signals from said rolling moment calculating means and said rolling moment distribution ratio calculating means, for calculating a lateral load shift quantity;   suspension reaction force variation calculating means responsive to output signal from said lateral load shift quantity calculating means, for calculating a variation in the reaction force of each suspension; and   control quantity calculating means responsive to output signal from said suspension reaction force variation calculating means for calculating a control quantity to adjust said valve means.   
     
     
       16. The system according to claim 15, further comprising: a longitudinal G-sensor provided on the vehicle for detecting longitudinal acceleration of the vehicle and for generating a longitudinal acceleration signal indicative thereof;   second hysteresis means for smoothing said longitudinal acceleration signal by hysteresis-processing said longitudinal acceleration signal;   second dead zone means for cutting the fluctuations of output signal from said second hysteresis means in the vicinity of zero;   longitudinal load shift quantity calculating means responsive to output signal from said dead zone means and said vehicle height signal for calculating a longitudinal load shift quantity;   suspension reaction force variation calculating means responsive to output signal from said longitudinal load shift quantity calculating means for calculating a variation in the reaction force of each of said suspensions, whereby said control quantity calculating means is responsive to output signal from said second suspension reaction force variation calculating means for calculating said control quantity.   
     
     
       17. The system according to claim 16, further comprising: second hysteresis width changing means responsive to said vehicle speed signal for changing a second predetermined hysteresis width to be applied to said longitudinal acceleration signal based on the magnitude of said vehicle speed, said second predetermined hysteresis width being set wider as said vehicle speed is larger.   
     
     
       18. The system according to claim 17, further comprising: dead zone width changing means responsive to said vehicle speed signal for changing a predetermined dead zone width to be applied to said output signal from said second hysteresis means based on the magnitude of said vehicle speed, said predetermined dead zone being set wider as said vehicle speed is larger.   
     
     
       19. The system according to claim 18, wherein said dead zone width changing means is applied to set said predetermined dead zone width wider than said second predetermined hysteresis width. 
     
     
       20. In a system for controlling an active suspension of a vehicle, having fluid suspensions provided for respective wheels, valve means for charging and discharging the fluid into and out of the respective fluid suspensions to extend and contract the suspensions independently, a vehicle speed sensor for sensing vehicle speed and for generating a vehicle speed signal indicative of the vehicle speed, a G-sensor for provided on the vehicle for detecting acceleration of the vehicle and for generating an acceleration signal indicative of the acceleration, hysteresis means for smoothing said acceleration signal by processing said acceleration signal with a predetermined hysteresis width, dead zone means for cutting the fluctuations of said acceleration signal within a predetermined dead zone width in the vicinity of zero, and controlling means responsive to said acceleration signal for controlling said valve means to adjust an amount of the fluid to be charged and discharged in said suspensions so as to control the vehicle attitude, the improvement of said system comprises: hysteresis width changing means responsive to said vehicle speed signal for changing said predetermined hysteresis width based on the magnitude of said vehicle speed, said predetermined hysteresis width being set wider as said vehicle speed becomes larger.